Prefer vtkDoubleArray::GetValue to GetTuple for single component arrays
Prefer vtkDoubleArray::GetValue to GetTuple for single component arrays

On a single component vtkDoubleArray, GetValue is significantly
faster than GetTuple and SetValue is faster than SetTuple.  These
changes result in about a 3% performance increase to the Gaussian
splatter filter since it is called in a deeply nested loop.

Change-Id: I88f6791667d57088e69a89e18a515196ba674af9

sumedhasingla/VTK,SimVascular/VTK,hendradarwin/VTK,mspark93/VTK,jmerkow/VTK,keithroe/vtkoptix,gram526/VTK,jmerkow/VTK,sankhesh/VTK,hendradarwin/VTK,sankhesh/VTK,gram526/VTK,keithroe/vtkoptix,msmolens/VTK,candy7393/VTK,ashray/VTK-EVM,demarle/VTK,hendradarwin/VTK,sankhesh/VTK,gram526/VTK,mspark93/VTK,sumedhasingla/VTK,gram526/VTK,candy7393/VTK,candy7393/VTK,candy7393/VTK,mspark93/VTK,demarle/VTK,keithroe/vtkoptix,SimVascular/VTK,keithroe/vtkoptix,msmolens/VTK,gram526/VTK,mspark93/VTK,msmolens/VTK,hendradarwin/VTK,demarle/VTK,ashray/VTK-EVM,hendradarwin/VTK,hendradarwin/VTK,ashray/VTK-EVM,gram526/VTK,SimVascular/VTK,sumedhasingla/VTK,candy7393/VTK,ashray/VTK-EVM,msmolens/VTK,candy7393/VTK,msmolens/VTK,SimVascular/VTK,sumedhasingla/VTK,keithroe/vtkoptix,sankhesh/VTK,sankhesh/VTK,ashray/VTK-EVM,jmerkow/VTK,msmolens/VTK,jmerkow/VTK,sumedhasingla/VTK,SimVascular/VTK,keithroe/vtkoptix,jmerkow/VTK,sumedhasingla/VTK,keithroe/vtkoptix,mspark93/VTK,mspark93/VTK,gram526/VTK,mspark93/VTK,ashray/VTK-EVM,ashray/VTK-EVM,gram526/VTK,sumedhasingla/VTK,sankhesh/VTK,jmerkow/VTK,jmerkow/VTK,demarle/VTK,hendradarwin/VTK,candy7393/VTK,ashray/VTK-EVM,SimVascular/VTK,SimVascular/VTK,keithroe/vtkoptix,demarle/VTK,msmolens/VTK,sankhesh/VTK,demarle/VTK,candy7393/VTK,mspark93/VTK,demarle/VTK,msmolens/VTK,jmerkow/VTK,demarle/VTK,sankhesh/VTK,SimVascular/VTK,sumedhasingla/VTK